1. Field of the Invention
The present invention relates generally to devices and methods for use with high-speed machining.
2. Description of the Prior Art
During the past decade, there has been a marked increase in the industrial use of high-speed machining technology. In addition, machining centers have been developed which are capable of spindle and slide speeds that are an order of magnitude higher than those available on conventional machining centers. For example, a number of different industrial suppliers have introduced reliable machining centers with slide speeds that approach or exceed 60 meters per minute, accelerations of 10 meters per second squared, and spindles capable of delivering in excess of 30 kilowatts of power to the cutting zone at spindle speeds greater than 30 thousand revolutions per minute. While these new machining centers offer the possibility of much higher material removal rates, markedly improved surface finish, and increased workpiece quality, their use also requires much more technical expertise than conventional machining centers. Regenerative chatter is one of the most difficult phenomena to master in high-speed machining because solutions are often counterintuitive; for example speeding up the spindle or increasing the overhang of the tool may actually diminish the tendency of the system to chatter. This behavior must be made intuitive to the programmers and machinists if high-speed machining centers are to be used to their full potential.
Various methods and devices for identifying, avoiding and controlling, chatter have been developed, such as described in Altintas et al., xe2x80x9cAnalytical Prediction of Stability Lobes in Milling in Annals of the CIRP (1995), 44(1): 357-362; U.S. Pat. No. 3,967,515 to Natchtigal, et al.; U.S. Pat. No. 4,170,103 to Rouch, et al; U.S. Pat. No. 5,033,340 to Siefring; U.S. Pat. No. 4,604,834 to Thompson; U.S. Pat. No. 3,938,626 to Hopkins; U.S. Pat. No. 4,759,243 to Thompson; and U.S. Pat. No. 5,170,358 to Delio. However, these devices and methods may be expensive and may require a substantial amount of expertise to use correctly.
It is therefore an object of the present invention to provide a device for stable speed determination in machining that does not require cutting tests.
It is another object of the present invention to provide a device for stable speed determination in machining that is suitable for integration with a machine-tool controller.
It is yet another object of the present invention to provide a device for stable speed determination in machining that allows the optimal speeds for a tool to be quickly downloaded and stored for later use.
It is yet another object of the present invention to provide a device for stable speed determination in machining that may be produced cheaply.
It is yet another object of the present invention to provide a device for stable speed determination in machining that may be made small and may be used by those with minimal expertise in machine-tool dynamics.
It is yet another object of the present invention to provide a device for stable speed determination in machining that may be made relatively robust with respect to a machining environment.
It is yet another object of the present invention to provide a device for stable speed determination in machining that may be used in combination with conventional chatter recognition and control schemes and xe2x80x9ctool-tuningxe2x80x9d strategies.
It is yet another object of the present invention to provide a device for stable speed determination in machining that does not rely on direct quantitative, experimental measurements of frequency response functions (FRFs) of the machine tool structure, and, furthermore, does not rely on curve fitting of such data.
It is yet another object of the present invention to provide a device for stable speed determination in machining that may make measurements on a rotating tool.
According to one aspect, the present invention provides a device for stable speed determination in machining, the device comprising: an excitation means for non-cuttingly exciting a rotating milling tool; and a measuring means for measuring the excitement of the milling tool by the excitation means.
According to a second aspect, the present invention provides a device for stable speed determination in machining, the device comprising: a rotating excitation means for non-cuttingly exciting a lathe tool; and a measuring means for measuring the excitement of the lathe tool by the excitation means.
According to a third aspect, the present invention provides a method for determining at least one stable speed for milling comprising the steps of: rotating a milling tool at a plurality of speeds; non-cuttingly exciting the milling tool; measuring the excitement of the milling tool at the plurality of speeds; determining at least one stable speed for the milling tool based on results from the measurement step.
According to a fourth aspect, the present invention provides: a method for determining at least one stable speed for lathe cutting comprising the steps of: rotating a lathe test bar at a plurality of speeds using a lathe spindle; non-cuttingly exciting a lathe tool using an excitation means mounted in the lathe test bar to measure the excitement of the lathe tool at the plurality of speeds; determining at least one stable speed for the lathe tool based on results from the measurement step.
Other objects and features of the present invention will be apparent from the following detailed description of the preferred embodiment.